I have pdf's to two solutions manuals for a textbook, and I'm trying to determine how much they differ by analyzing both copies with some sort of tool. Does such a thing exist? Is there any other way of determining the differences between two OCR PDF documents?
I've done it by converting each PDF to Word, for which there are a bunch of free converters online. Then I use Word's file comparison feature to see the differences: http://support.microsoft.com/kb/306484
One possibility would be Acrobat (Pro), which has a compare function.
If it is for comparing the results of the OCR process, you might export both documents to Text, and use a text editor which has a compare function (such as Textwrangler or BBEdit).
diffpdf on linux. You can download a Ubuntu live CD and use that, but since
diffpdf is not included in the default install you have to install it with the software center